Rodents

The House Mouse

(Mus musculus)

Is a small, slender rodent that has a slightly pointed nose; small, black, somewhat protruding eyes; large, scantily haired ears, and a nearly hairless tail with obvious scale rings. The adult mouse weighs about 2/5 to 4/5 ounces. They are generally grayish-brown with a gray or buff belly. Similar mice include the white-footed mice and jumping mice( which have a white belly), and harvest mice (which have grooved upper incisor teeth.) 

Habitat: House mice live in and around homes, farms, commercial establishments, as well as in open fields and agricultural lands. The onset of cold weather each fall in temperate regions is said to cause mice to move into structures in search of shelter and food.

Food Habits: House mice eat many types of food but prefer seeds and grain. They are not hesitant to sample new foods and are considered "nibblers," sampling many kinds of items that may exist in their environment. Foods high in fat, protein, or sugar may be preferred even when grain and seed also are present. Such items include bacon, chocolate candies, butter and nutmeats. A single mouse eats only about 3 grams of food per day (8 pounds per year) but because of their habit of nibbling on many foods and discarding partially eaten items, mice destroy considerably more food than they consume

General Biology, Reproduction, and Behavior: House mice are mainly nocturnal, although at some locations considerable daytime activity may be seen. Seeing mice during daylight hours does not necessarily mean there is a high population present, although this usually is true for rats Mice have poor eyesight, relying more on their hearing and their excellent senses of smell, taste and touch. They are considered essentially colour-blind.

House mice can dig and may burrow into the ground in fields or around structures when other shelter is not readily available. Nesting may occur here or in any sheltered location. Nests are constructed of fibrous materials and generally have the appearance of a "ball" of material loosely woven together. These nests are usually 4 to 6 inches in diameter.  Litters of 5 or 6 young are born 19 to 21 days after mating, although females that conceive while still nursing may have a slightly longer gestation period.

Mice may breed year-round and a female may have 5 to 10 litters per year. Mouse populations can therefore grow rapidly under good conditions, although breeding and survival of young slow markedly when population densities become high.

During its daily activities, a mouse normally travels an area averaging 10 to 30 feet in diameter, seldom traveling further than this to obtain food or water

The roof rat

(Rattus Rattus)

Rattus Rattus is commonly known as the roof rat, black rat or ship rat. Roof rats were common on early sailing ships and apparently arrived in this country by that route. This rat has a long record as a carrier of plague.

It is about 7-10 inches long and weighs about 5-9 ounces. The Roof Rat has a long tail which is longer than the combined length of the head and body. The Roof Rats have pointed noses and large ears.

Habitat: Roof rats are more aerial than Norway rats in their habitat selection and often will live in trees or on vine covered fences. Landscaped residential or industrial areas provide good habitat, as does vegetation of riverbanks and streams. They will often move into sugarcane and citrus groves. Roof rats are sometimes found living in or around poultry or other farm buildings as well as in industrial sites where food and shelter are available. Being agile climbers, Roof rats frequently enter buildings from the roof or accesses near utility lines which they use to travel from area to area.

Feeding Habits: The food habits of roof rats resemble those of tree squirrels, since they both like a wide variety of fruit and nuts. They also feed on a variety of ornamental and native plant materials. Like the Norway rat, they are omnivorous and will feed on most anything if necessary. Roof rats usually require water daily, though their local diet may provide an adequate amount if high in water content.

Reproduction and Development: Born in a nest about 21 to 23 days after conception, the young rats are naked and their eyes are closed. The 5 to 8 young in the litter develop rapidly, growing hair within a week. When they are 9 to 14 days old, their eyes open and they begin to explore for food and move about near their nest. In the third week they begin to take solid food. The number of litters depends on the area and varies with nearness to the limit of their climatic range, availability of nutritious food, density of the local rat population and age of the rat. The young may continue to nurse until 4 or 5 weeks old. Young rats generally cannot be trapped until about 1 month old. At about 3 months of age they are completely independent of the mother and are reproductively mature

Feeding Behaviour: Roof rats usually begin searching for food shortly after sunset. If the food is in an exposed area and too large to be eaten quickly, yet not too large to be moved, they will usually carry it to a hiding place before eating it. Many rats will cache or hoard considerable amounts of solid food, which they may or may not eat later. When necessary, roof rats will travel considerable distances for food. They can often be seen at night running along overhead utility lines. They may live in trees or attics and climb down to a food source. Roof rats have a strong tendency to avoid new objects in their environment and this can influence control efforts. These rats may take several days before they will approach a bait station or trap.

The Norway rat

(Rattus norvegicus)

Is a stocky burrowing rodentThe Norway rat is found generally at lower elevations but may be found wherever humans live.Also called the brown rat, house rat, barn rat, sewer rat, gray rat, or wharf rat, it is a slightly larger animal than the roof rat.  The nose is blunt, the ears are small, close set and do not reach the eyes when pulled down.  The tail is scaly, semi-naked and shorter than the head and body combined.  When distinguishing the Norway rat from the Roof rat, pull the tail back over the body.  The tail of the Roof rat will reach the nose.  The tail of the Norway rat will not reach beyond the ears.  Adult Norway rats weigh an average of about 1 pound. Their fur is coarse and usually is brownish or reddish-gray above, and whitish-gray on the belly. Blackish individuals occur in some locations.

Habitat : Norway rats live in close association with people.  They burrow to make nests under buildings and other structures, beneath concrete slabs, along stream banks, around ponds, in garbage dumps, and at other locations where suitable food, water and shelter are present.  On farms they may inhabit barns, granaries, livestock buildings, silos, and kennels. In urban or suburban areas they live in and around residences, in cellars, warehouses, stores, slaughterhouses, docks, and in sewers.  Although they can climb, Norway rats tend to inhabit the lower floors of multi-story buildings.

Food Habits : Norway rats will eat nearly any type of food.  When given a choice, they select a nutritionally balanced diet, choosing fresh, wholesome items over stale or contaminated foods.  They prefer cereal grains, meats and fish, nut, and some types of fruit. Rats require 1/2 to 1 ounce of water daily when feeding on dry foods but need less when moist foods are available. Food items in household garbage offer a fairly balanced diet and also satisfy their moisture needs.

General Biology, Reproduction and Behaviour: Norway rats are primarily nocturnal.  They usually become active about dusk, when they begin to seek food and water.  Some individuals may be active during daylight hours when the rat population is high, when disturbed (weather change, construction, etc.) or when their food source is threatened.
The territories of most rats are between 50 and 150 feet radius of the nest.  In populations where there are many rats and abundant food and shelter, the territories will be towards the lower end of the range.  If need be, however, rats will travel 300 feet or more daily to obtain their food and water.   In urban areas most rats remain around the buildings and yards which provide their necessities, and unless they are disturbed, they do not move great distances.

Norway rats usually construct nests in below-ground burrows or at ground level

Litters of 6 to 12 young are born 21 to 23 days after conception.  Newborn rats are naked and their eyes are closed, but they grow rapidly, eating solid food at 2 1/2 to 3 weeks.  They become completely independent at about 3 to 4 weeks and reach reproductive maturity at 3 months of age, sometimes as early as 8 weeks. Female Norway rats may come into heat every 4 or 5 days, and they may mate within a day after a litter is born.
The average female rat has 4 to 6 litters per year and may successfully wean 20 or more offspring annually.